This invention relates to cylinder heads for internal combustion engines with compression ignition, of the type having precombustion chambers, intake and exhaust ports, and valve guides and seats respectively associated with the cylinders of the engine.
It is known in the manufacture of cylinder heads, cast or not under pressure, to use molded cores to form intake and exhaust ports and to insert valve seats and precombustion chambers into this cylinder head.
French Pat. No. 2,165,646 describes a typical example of this inserted valve seat, intended to be attached in the cylinder heads of internal combustion engines. This valve seat has a self-tapping thread.
French Pat. Nos. 2,393,147 and 2,393,148 show internal combustion engines of the diesel type with an injection and ignition precombustion chamber in which the precombustion chamber is made in a mounted part inserted into the cylinder head.
It is also known from British Pat. No. 1,075,951 how to make intake and exhaust ports using refractory metal inserts one of whose ends is shaped so as to constitute a valve seat.
Moreover, West German Pat. No. 2,602,434 emphasizes the essential advantage that the insert offers during the casting of a cylinder head for an internal combustion engine, i.e. intake and exhaust ports covered with a ceramic material make possible a good heat insulation.
In French Pat. No. 2,423,643, a heat conducting insert plate is used which has a hollow space between the seats and enlarged areas thoroughly applied on the thoroughly cooled areas of the cylinder head to protect the areas between the seats and to remove the heat.
Current manufacturing techniques do not make it possible to manufacture a particularly simple and economical cylinder head for a diesel type engine with precombustion chambers, to the extent that the precise machining of this cylinder head makes it difficult and costly to insert the precombustion chamber or the valve seats.